What can I do when trees or shade block my solar panels — and what can my neighbor do?

The rule

Trees and buildings can shade a solar system, and the legal question is usually not
"does my neighbor have to cut the tree?" but "which rule applies, and when did each side's
interest begin?" California's answer is the Solar Shade Control Act,
Public Resources Code sections 25980 through 25986.
Section 25980 gives the Act its name and states its policy: the state encourages trees and
shrubs for shade and other benefits, while recognizing that the widespread use of solar
collectors "requires specific and limited controls on trees and shrubs."

The core limit is in
section 25982:
after the installation of a solar collector, a person owning or in control of another
property may not allow a tree or shrub to be placed — or, if placed, to grow — on that
property so as to cast a shadow greater than 10 percent of the collector absorption
area upon the collector surface at any one time between 10 a.m. and 2 p.m., local
standard time.

What the rule means in practice

• Timing decides most cases. The 10 percent limit applies to trees placed or grown
  after the collector's installation. A tree that predates the collector is generally
  outside the provision.
• The test is specific. It is not "any shade at any time" — it is more than 10
  percent of the collector absorption area, at any one time, between 10 a.m. and 2 p.m.
  local standard time.
• The obligation sits on the neighboring owner. The section applies to "a person
  owning or in control of another property" — the person who allows the tree to be placed
  or to grow there.
• Passive and natural systems have their own rule. Section 25986 lets a person who
  plans a passive or natural solar heating or cooling system that would affect an
  adjacent active solar system seek equitable relief to exempt the passive system, where
  the court finds it would provide demonstrably greater net energy savings.

What may still be required or restricted

• Local tree ordinances can regulate planting, trimming, and removal, and local
  governments may administer the Act through their own processes.
• Recorded solar easements can protect access to sunlight against future trees or
  buildings, but only if they exist for the property.
• Oregon takes a different path. Oregon protects solar access mainly through solar
  energy easements: ORS 105.885 defines terms, ORS 105.890 makes the easement appurtenant
  and addresses termination, and ORS 105.895 sets the requirements for creating the
  easement by recorded instrument. Separately, ORS 105.880 voids a conveyance that
  prohibits the use of a solar energy system.
• Homeowners association rules can govern trees on association or common property,
  within the limits of state law — including the solar-rights limits of statutes like
  California Civil Code section 714, which voids governing-document provisions that
  effectively prohibit or restrict a solar energy system.
• Other states differ again. A rule that applies in California or Oregon does not
  apply elsewhere without checking that state's statutes.

Facts that could change the answer

• When the tree or shrub was placed or began growing, versus when the collector was
  installed.
• Whether the tree stands on private land, public land, or association property.
• Whether a local ordinance or a recorded solar easement applies.
• Whether the system is active or passive/natural, for the section 25986 exemption.
• Whether the property is in an HOA or common interest development.

Practical decision path

1. Confirm which state's law applies and read that state's solar-access provisions.
2. Determine the collector's installation date and the tree's planting or growth date.
3. Check the local tree ordinance, any recorded solar easement, and any HOA rules.
4. Document the shading with dated photographs before taking any action.
5. Talk to the neighbor first; most disputes are resolved by agreement, and both sides
   face legal risk in litigation.

Before work begins, obtain the written requirement from the authority named in the guide and keep the record.

Records to keep

Keep the installation date and paperwork for the solar system, any documentation of the
tree's planting date, the local tree ordinance, any recorded easement or HOA rule, and
dated photographs of the shading. These records are what a court or mediator will use to
apply the statute's timing rules.

When professional advice may help

Solar-shade disputes turn on dates, local ordinances, easements, and property boundaries.
Consider advice from an attorney familiar with solar-access and property law in the state
where the property is located before cutting a neighbor's tree or filing a claim.